Electronic devices face continued pressure to design and produce their configurations in a further state of miniaturization, ergonomically pleasing shapes, and a reduced weight. To achieve these goals, many choices in materials of construction and shape must be exercised during upstream manufacturing. Whenever changes occur in the product, invariably there are also changes in tooling. Retooling a fabrication facility requires significant time and cost for requalification. For electronic manufacturing, the substrate must be held uniformly in place during several process steps, including lithography and deposition. Thin solid materials are typically held in place by affixing to a rigid carrier. Carrier substrates may be composed of sapphire, quartz, certain glasses, or silicon, exist in thicknesses from 0.5-1.5 mm (500-1,500 μm), and be of larger area than the thin solid material. Challenges exist in choosing a means of adhesion that offers sufficient adhesive force and quality to withstand the manufacturing process, while allowing the thin solid materials to be easily removed without damaging their integrity.
Several alternative thin solid materials are being considered for use in manufacturing. Conventional glass substrates used in the manufacture of displays are being reduced in thickness to 0.1 mm (100 μm) or less. In some cases, alternatives to glass are being considered, including non-glass inorganic and organic materials that exhibit intrinsic properties to support the application of layered metal and dielectric patterns onto its surface to a sufficient level necessary to produce an electronic device. In some cases, the thin solid material not only supports the laminated electronic layers but also offers sufficient tensile strength and ductility and/or elasticity to allow bending of the substrate in configurations necessary to classify it as a flexible display. These thin solid materials may vary in thickness to as high as 100 μm or to below 10 μm. Whether the material is glass or ceramic, metal, organic, or a composite, they require certain care in the handling, affixing, and removal from carrier substrates. It is well known that as material type, thickness, and shape varies, the method and means to handle such units will also vary. For example, the handling of a 12″ diameter round piece of domestic type aluminum metal foil (e.g. thickness 2 mil, ˜50 μm), although it will wrinkle, is easier to handle than the same size and thickness of silicon, which is prone to cracking and breaking and is unable to support its own weight. As the need for adjusting the tooling and support required to handle thin solid materials, so also exists the demand for adhesives that exhibit a range in adhesive force, or the ability to tune adhesion.
Common tape adhesives do not adequately support thin solid materials with the necessary rigidity and uniformity to meet electronic processing objectives. The tape adhesive is much too elastic for mechanical stability during certain manufacturing steps such as polishing or grinding. Additionally, the composition of many tapes are based upon acrylic or silicone chemistry and are observed to exhibit outgassing (weight loss) due to material degradation at elevated temperatures at or above 400° C. The characteristic of outgassing will cause gas bubbles in-between the carrier substrate and the thin solid material which deforms the surface of the thin material, and in severe instances, will perforate the surface to cause catastrophic damage to the sensitive circuitry deposited upon the surface. For both mechanical and thermal resistance, there is a need for a system that can be inserted between two hard substrates and achieve the necessary thermal and chemical resistance requirements of the customer process. In this case, a thermal resistance that reaches 400° C. or more is necessary. To this end, it is desired to have an adhesive which offers sufficient thermal and chemical resistance to support electronic manufacturing processes for display operations and is easy to remove by tensile pulling (peeling) from the substrate to reveal a film with a built electronic structure.